nikki carb question...

[oldntired55]

i recently upgraded a troy bilt rider with a knocking 18hp Intek...with a strong & quiet 20hp v twin. it is belching black smoke, after a carb teardown and immersed in my ultrasonic cleaner for 2 cycles... i have found clogged passages in the upper main body before, but this one is spotless. i am curious about 2 things, one, could the fuel be running past the needle and seat, both look good upon close inspection with a magnifier... all emulsion tubes and low speed jets are clear with a flashlight. its puzzling because it will start right up, then start the black smoke and running rough. when it runs clean, it runs great. my other question, upon teardown i noticed the fuel transfer tube has one hole open, the other blocked with a small plug, i have another nikki off a 25 hp twin,l that tube has both openings open. which is correct? or should they all have a ball plug in them? i am attaching pics... this carb in question is off this model # 407777- 0128-E1 ...any help on this???

 

[oldntired55]

also, the gasket under the venturi is fine... checked that tonight...

 

[ILENGINE]

I would say both of those passages should have a ball plug in them to prevent unmetered fuel from bypassing the jet in the brass piece that fits in the bottom.

 

[oldntired55]

THAT was just my thought, i also have a Nikki carb on my DLT 25hp v twin. that particular carb has the white fuel transfer tube with 2 individual jets. i have some #9 shot in my reloading room, im going to plug those 2 passages and try it! thanks for the input

 

[oldntired55]

Great, i closed up those holes in the transfer tube... not, it starts and runs clean.. but now i have picked up a 1/2 throttle surge... now what? i have set , and reset governor ,,,, could the governor spring be weak? this engine sat idle for quite a few years